1. Field of the Invention
The invention relates to a combination of a secondary long chained aliphatic amine admixed with known wax crystal modifiers, usch as ethylene containing copolymers, for improving the cold flow properties of distillate fuel oil.
2. Description of the Prior Art
Various patents have taught the use of alkyl amines as additives for distillate fuel oils, primarily as anti-rust agents or to inhibit the formation of sediment or corrosion. Examples of such patents include U.S. Pat. No. 2,684,292 which teaches amine with at least 14 carbons as a sludge inhibitor in fuel oils containing cracked components; U.S. Pat. No. 2,672,408 which teaches amines as color stabilizers for distillate fuel oils; U.S. Pat. No. 2,456,569 wherein amines are used to stabilize diesel fuel against gum formation; U.S. Pat. No. 2,550,981 wherein amines are used to inhibit fogging of fuels in the presence of water and British Pat. No. 714,178 which teaches branched amines as color stabilizers in fuel oil.
Kerosene, which acts as a solvent for n-paraffin wax, had traditionally been a component of middle distillate fuel oils. Recently, with the increased demands for kerosene for use in jet fuels, the amount of kerosene used in middle distillate fuel oils has decreased. This, in turn, has frequently modifiers, the addition of wax crystal modifieres, e.g. pour point depressant additives, to the fuel oil to make up for the lack of kerosene. The more effective of these distillate oil pour depressants are copolymers of ethylene with various other monomers, e.g. copolymers of ethylene and vinyl esters of lower fatty acids such as vinyl acetate (U.S. Pat. No. 3,048,479); copolymers of ethylene and alkyl acrylate (Canadian Pat. No. 676,875); terpolymers of ethylene with vinyl esters and alkyl fumarates (U.S. Pat. Nos. 3,304,261 and 3,341,309); polymers of ethylene with other lower olefins, or homopolymers of ethylene (British Pat. Nos. 848,777 and 993,744); chlorinated polyethylene (Belgium Pat. No. 707,371 and U.S. Pat. No. 3,337,313); etc. However, in general, these ethylene backbone pour point depressants, while very effective in lowering the pour point of distillate oil, sometimes result in wax crystals having large particle sizes ranging from 1 millimeter up to an inch in their larger dimensions. These large particles tend to be filtered out by the screens and other filter equipment normally used in the fuel path of middle distillate fuel oil powered prime movers, e.g. diesel powered trucks, with a resulting plugging of these screens and filters even though the temperature of the oil is substantially above its pour point.
In my prior patent, U.S. Pat. No. 2,852,467, it was found that fatty acid salts of alkylene imine polymers were effective as pour point depressants in lubricating oil. Also, in U.S. Pat. No. 3,166,387, it was found that certain fatty acid salts of a secondary or tertiary monoamine having at least two C.sub.10-22 alkyl groups, were effective as pour point depressants in distillate fuel oils. In my recently issued patent, U.S. Pat. No. 3,658,493, it was reported that certain fatty acid salts of a secondary or tertiary monoamine having at least two C.sub.10-22 alkyl groups, were effective as pour point depressants in distillate fuel oils.
The low temperature flowability of a middle distillate fuel oil has been improved by the addition of a minor amount of an essentially saturated hydrocarbon fraction which is substantially free of normal paraffinic hydrocarbons and having number average molecular weight of from about 600 to about 3000 alone (U.S. Pat. No. 3,660,058) and in combination with: a copolymer of ethylene and an unsaturated ester (U.S. Pat. No. 3,790,359); a polymeric pour depressant of number average molecular weight within the range of about 800 and about 50,000 (U.S. Pat. No. 3,773,478); and either a polymer containing halogenated polymethylene segments or an N-aliphatic hydrocarbyl succinamic acid or derivative thereof (U.S. Pat. No. 3,846,093).
U.S. Pat. No. 3,419,395 teaches hydrogenated copolymers of butadiene and styrene as pour point depressants for distillate fuel oils.
It is also known to lower the pour point and improve the pumpability of distillate fuel oils by the addition of ethylene homopolymers and copolymers of ethylene with an olefinic monomer having from 3 to 6 carbon atoms (British Pat. No. 993,744) e.g. propylene (British Pat. No. 848,777).